U.S. patent number 8,708,277 [Application Number 13/899,172] was granted by the patent office on 2014-04-29 for method and apparatus for automated launch, retrieval, and servicing of a hovering aircraft.
This patent grant is currently assigned to Aerovel Corporation. The grantee listed for this patent is Aerovel Corporation. Invention is credited to Brian T. McGeer, Andreas H. von Flotow.
United States Patent |
8,708,277 |
McGeer , et al. |
April 29, 2014 |
Method and apparatus for automated launch, retrieval, and servicing
of a hovering aircraft
Abstract
Various embodiments of the present disclosure provide an
apparatus configured to automatically retrieve, service, and launch
an aircraft. For retrieval, the aircraft drops a weighted cable,
and pulls it at low relative speed into a broad aperture of the
apparatus. In certain instances, the cable is dragged along guiding
surfaces of the apparatus into and through a slot until its free
end is captured. The aircraft becomes anchored to the apparatus,
and is pulled downward by the cable into a receptacle. Guiding
surfaces of the receptacle adjust the position and orientation of a
probe on the aircraft, directing the probe to mate with a docking
fixture of the apparatus. Once mated, the aircraft is automatically
shut down and serviced. When desired, the aircraft is automatically
started and tested in preparation for launch, and then released
into free flight. A full ground-handling cycle is thus accomplished
with a simple, economical apparatus.
Inventors: |
McGeer; Brian T. (Underwood,
WA), von Flotow; Andreas H. (Hood River, OR) |
Applicant: |
Name |
City |
State |
Country |
Type |
Aerovel Corporation |
White Salmon |
WA |
US |
|
|
Assignee: |
Aerovel Corporation (White
Salmon, WA)
|
Family
ID: |
42101759 |
Appl.
No.: |
13/899,172 |
Filed: |
May 21, 2013 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
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13743069 |
Jan 16, 2013 |
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12702935 |
Feb 9, 2010 |
8453966 |
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61152076 |
Feb 12, 2009 |
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Current U.S.
Class: |
244/110F;
244/110C; 244/63; 244/110E |
Current CPC
Class: |
B64C
39/024 (20130101); B64F 5/00 (20130101); B64F
1/12 (20130101); B64F 5/40 (20170101); B64C
25/68 (20130101); B64F 1/02 (20130101); B64F
1/06 (20130101); B64F 1/28 (20130101); B64F
1/04 (20130101); B64F 1/125 (20130101); B64C
2201/024 (20130101); B64C 2201/084 (20130101); B64C
2201/182 (20130101) |
Current International
Class: |
B64F
1/02 (20060101) |
Field of
Search: |
;244/110F,110C,63,1R,116,110E |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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781808 |
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Apr 1968 |
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CA |
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839101 |
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Apr 1970 |
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CA |
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0 472 613 |
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Apr 1992 |
|
EP |
|
Other References
A miniature powerplant for very small, very long range autonomous
aircraft, S.P. Hendrickson and. T. McGeer, Final Report under U.S.
DoE contract No. DE-FG03-96ER82187, Sep. 29, 1999 (25 pages). cited
by applicant .
Aerosonde hazard estimation, T. M.cGeer, 1994 (7 pages). cited by
applicant .
Aerosonde Pacific reconnaissance: ready when you are!, T. MeGeer,
Pacific Northwest Weather Workshop, Mar. 2005 (15 pages). cited by
applicant .
An Airspeed Vector Sensor for V/STOL Aircraft, E, Durbin and T.
McGeer, Journal of Aircraft, vol. 19, No, 6, Jun. 1982 (7 pages).
cited by applicant .
Automated Launch, Recovery, and Refueling for Small Unmanned Aerial
Vehicles, K. Mullens, et al., 2004 (11 pages). cited by applicant
.
Autonomous Aerosondes for Economical Atmospheric Soundings Anywhere
on the Globe, G.J. Holland, T. McGeer and H.H. Youngren, Bulletin
of the American Meteorological Society, vol. 73, No. 12, Dec. 1992
(12 pages). cited by applicant .
European Search Report for European Patent Application No.
10250229.1, dated Jan. 21, 2013 (5 pages). cited by applicant .
Examiner's First Report for Australian Patent Application No.
2007347147, dated Oct. 26, 2011 (2 pages). cited by applicant .
Flexrotor Long-Endurance VTOL Aircraft Transitions to Wing-Borne
Flight, available at
http://www.aerovelco.com/papers/FlexrotorTransitionsAnnouncement.pdf,
dated Aug. 4, 2011 (2 pages). cited by applicant .
International Search Report (PCT/US2007/076276), dated Sep. 22,
2008 (7 pages). cited by applicant .
Laima: The First Atlantic Crossing by Unmanned Aircraft, T. McGeer,
Feb. 25, 1999 (25 pages). cited by applicant .
Quantitative Risk Management as a Regulatory Approach to Civil
UAVs, T. MeGeer L. Newcombe, and J. Vagners, International Workshop
on UAV Certification, Jun. 4, 1999 (11 pages). cited by applicant
.
Regulatory Issues Involving Long-Range Weather Observation by
Aerosonde Autonomous Aircraft, T. McGeer, Oct. 9, 1998 (8 pages).
cited by applicant .
Safety, Economy, Reliability and :Regulatory Policy for Unmanned
Aircraft, T, McGeer, Mar. 2007 (9 pages). cited by applicant .
The Beartrap--A Canadian Invention, Crowsnest Magazine, vol. 17,
Nos. 3 and 4 [online], Mar.-Apr. 1965, [retrieved on Sep. 14,
2007]. Retrieved from the Internet at <URL:
http://www.readyayeready.comftimelinef1960s/beartrapfindex.htm>
(4 pages). cited by applicant .
Wide-Scale Use of Long-Range Miniature Aerosondes Over the World's
Oceans, T. McGeer and J. Vagners, 1999 (25 pages). cited by
applicant .
Written Opinion (PCT/US2007/076276), dated Mar. 5, 2009 (6 pages).
cited by applicant .
Skyhook (Harrier handling system); Harpoon Head Quarters; available
at http://www.harpoondatabases.com/encyclopedia/Entry2979.aspx;
printed Jun. 21, 2013 (3 pages). cited by applicant.
|
Primary Examiner: Ellis; Christopher P
Assistant Examiner: Badawi; Medhat
Attorney, Agent or Firm: Neal, Gerber & Eisenberg
LLP
Parent Case Text
PRIORITY CLAIM
This application is a continuation of, and claims priority to and
the benefit of, U.S. patent application Ser. No. 13/743,069, filed
on Jan. 16, 2013, which is a continuation of, and claims priority
to and the benefit of, U.S. patent application Ser. No. 12/702,935,
filed on Feb. 9, 2010, which claims priority to and the benefit of
U.S. Provisional Patent Application No. 61/152,076, filed on Feb.
12, 2009, now expired, the entire contents of each of which are
incorporated herein by reference.
Claims
The invention is claimed as follows:
1. A method for retrieving a flying object from free flight, said
method comprising: (a) causing a member connected to a body of the
flying object to be received in a slot defined by two spaced-apart
upwardly extending members supported by a base; (b) thereafter,
translating the flying object relative to the base toward a docking
station supported by the base; and (c) receiving a portion of the
flying object in the docking station.
2. The method of claim 1, wherein the two upwardly extending
members are configured to define the slot such that the slot is
configured to receive the member in the form of a string.
3. The method of claim 1, which includes securing the flying object
using at least one locking device of the docking station.
4. The method of claim 1, which includes servicing the flying
object using at least one connector.
5. The method of claim 4, wherein said servicing is performed
automatically.
6. The method of claim 1, which includes facilitating launch of the
flying object using at least one launch orienting device.
7. The method of claim 1, wherein each of the members supported by
the base is petal-shaped.
8. The method of claim 1, which includes measuring a
three-dimensional position of the flying object relative to the
base.
9. The method of claim 1, which includes measuring an orientation
of the flying object relative to the base.
10. A method for retrieving a flying object from free flight, said
method comprising: (a) causing a wing connected to a body of the
flying object to be received in one of a plurality of different
sets of slots defined by a plurality of spaced-apart upwardly
extending members supported by the base; and (b) receiving the
flying object in a docking station supported by the base.
11. The method of claim 10, which includes securing the flying
object using at least one locking device of the docking
station.
12. The method of claim 10, which includes servicing the flying
object using at least one connector.
13. The method of claim 12, wherein said servicing is performed
automatically.
14. The method of claim 10, which includes facilitating launch of
the flying object using at least one launch orienting device.
15. The method of claim 10, wherein each of the members is
petal-shaped.
16. The method of claim 10, which includes measuring a
three-dimensional position of the flying object relative to the
base.
17. The method of claim 10, which includes measuring an orientation
of the flying object relative to the base.
18. A method for retrieving a flying object from free flight, said
method comprising: (a) causing a member connected to a body of the
flying object to be received in a slot defined by two spaced-apart
arms extending transversely from a base, each arm including a
member extending transversely therefrom; (b) thereafter,
translating the flying object relative to the base toward a docking
station supported by the base; and (c) receiving a portion of the
flying object in the docking station.
19. The method of claim 18, wherein the two upwardly extending
members are configured to define the slot such that the slot is
configured to receive the member in the form of a string.
20. The method of claim 18, which includes securing the flying
object using at least one locking device of the docking
station.
21. The method of claim 18, which includes servicing the flying
object using at least one connector.
22. The method of claim 21, wherein said servicing is performed
automatically.
23. The method of claim 18, which includes facilitating launch of
the flying object using at least one launch orienting device.
24. The method of claim 18, which includes measuring a
three-dimensional position of the flying object relative to the
base.
25. The method of claim 18, which includes measuring an orientation
of the flying object relative to the base.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
The present application relates to the following commonly-owned
co-pending patent applications: U.S. patent application Ser. No.
13/717,147, filed on Dec. 17, 2012; U.S. patent application Ser.
No. 13/037,436, filed on Mar. 1, 2011; U.S. patent application Ser.
No. 13/527,177, filed on Jun. 19, 2012; U.S. patent application
Ser. No. 12/702,935, filed on Feb. 9, 2010; and U.S. patent
application Ser. No. 13/743,069, filed on Jan. 16, 2013.
BACKGROUND
1. Field of Invention
The present invention addresses launch, retrieval, and servicing of
a hovering aircraft, especially in turbulent winds or onto an
irregularly-moving surface, such as the deck of a ship in a rough
sea. Various embodiments of the present invention are especially
suited to unmanned aircraft of small size. These embodiments allow
for a fully automated operations cycle, whereby the aircraft can be
repeatedly launched, retrieved, serviced, and re-launched, without
manual intervention at any point, and while requiring only modest
accuracy in piloting.
2. Description of Problem
Hovering aircraft, be they helicopters, thrust-vectoring jets,
"tail-sitters", or other types, usually land by gently descending
in free thrust-borne flight onto a landing surface, coming to rest
on an undercarriage of wheels, skids, or legs. This elementary
technique can be problematic in certain situations, such as when
targeting a small, windswept landing pad on a ship moving in a
rough sea. Decades ago, the Beartrap or RAST system was developed
to permit retrieval with acceptable safety in such conditions.
Retrieval with this system involves securing a line between a
helicopter and landing deck, and then winching the helicopter down
onto a trolley. The helicopter is fastened to the trolley. After
retrieval, the trolley is used to move the helicopter along the
deck. The system is effective and widely used, but requires an
expensive and substantial plant in the landing area, as well as
manual operations coordinated between helicopter and shipboard
crew. Furthermore, the helicopter must carry a complete
undercarriage in addition to the necessary Beartrap components.
Desirable improvements relative to the Beartrap system include (a)
simplification of the apparatus, and (b) automated rather than
manual operation. Ideally not only would retrieval but also
subsequent refueling and launch would be automated. This would be
particularly desirable for an unmanned aircraft, whose operations
cycle could then be made fully autonomous. Some experimental work
toward this objective has been done for a hovering aircraft, as
described in the publication by Mullens et al. titled, "Automated
Launch, Recovery, and Refueling for Small Unmanned Aerial Vehicles"
(2004); however, success has been limited even with light wind and
a stationary base. The present invention by contrast provides for
fully automated operation in calm or rough conditions, using
apparatus which is simple, portable, and suitable for a small
vessel or similarly confined base.
SUMMARY
In one embodiment of the method of the present invention, an
aircraft would proceed automatically from free thrust-borne flight
to retrieval to launch through the following sequence of actions:
(a) while approaching a base at low relative speed, the aircraft
drops a weighted cable; (b) the aircraft then flies over a
retrieval apparatus, which brings the cable into an aperture of
cable guides, which in one embodiment forms the shape of a V in the
horizontal or substantially horizontal plane; (c) further
translation pulls the cable into and through a slot at the terminus
of the cable guides, which captures the cable; (d) the aircraft is
then anchored; (e) if the cable is not captured, the aircraft can
climb away and return for another approach; (f) the aircraft,
recognizing capture of the cable by an increase in tension,
winches-in the cable and so draws itself into a docking receptacle,
such as, in one embodiment, a funnel-like receptacle at the vertex
of the cable guides; (g) as the aircraft is drawn into the docking
receptacle, guiding surfaces align and ultimately mate the aircraft
with one or more connectors for docking and servicing; (h) the
cable is released from the retrieval apparatus, and retracted by
the aircraft; (i) the aircraft is shut-down, refueled and otherwise
serviced as necessary through one or more suitable connectors; (j)
the aircraft completes launch preparations, and develops sufficient
thrust to accelerate away from the retrieval apparatus when
released; and (k) the aircraft is released into thrust-borne free
flight.
Since loads can be low during retrieval from hover, the apparatus
can be light and portable. Furthermore, easy targeting makes the
technique well-suited for both manual control and economical
automation.
It should be appreciated that the apparatus of various embodiments
of the present invention include an aircraft docking assembly
attached to an aircraft, a base retrieval apparatus attached to a
stationary or movable base, and the combination of these configured
so as to accomplish the methods of the present invention.
Additional features and advantages are described herein, and will
be apparent from the following Detailed Description and the
Figures.
BRIEF DESCRIPTION OF THE FIGURES
FIGS. 1A, 1B, 1C and 1D are a series of diagrammatic rear-quarter
perspective views of an embodiment of the present invention for a
helicopter, illustrating an aircraft docking assembly attached to
the helicopter, a base retrieval apparatus or servicing station,
and the helicopter sequentially entering, capturing, docked in, and
launching from the base retrieval apparatus or servicing
station.
FIG. 2 is an enlarged partially fragmentary perspective view of a
the base retrieval apparatus or servicing station for capturing,
docking, servicing, and launching a helicopter.
FIGS. 3A, 3B, 3C and 3D are a series of diagrammatic rear-quarter
perspective views of an embodiment of the present invention for a
hovering "tail-sitter" aircraft, illustrating an aircraft docking
assembly attached to the aircraft, a base retrieval apparatus or
servicing station, and the aircraft sequentially entering,
capturing, dOcked in, and launching from the base retrieval
apparatus or servicing station.
FIG. 4 is an enlarged perspective view of a representative docking
probe mounted in the tail of a "tail-sitter" aircraft of one
embodiment of the present invention.
FIG. 5 is a perspective view of a representative aircraft as in
FIG. 4 being pulled into a docking receptacle of the base retrieval
apparatus of one embodiment of the present invention.
FIGS. 6A, 6B, 6C and 6D are a series of diagrammatic rear-quarter
perspective views of an embodiment of the present invention for a
hovering aircraft, illustrating a possible downwind retrieval and
launch sequence.
DETAILED DESCRIPTION
Various embodiments of the present invention are generally directed
to apparatus and methods for retrieving a flying object or an
aircraft from substantially thrust-borne free flight. In one
embodiment, the apparatus includes an aircraft docking assembly for
a helicopter and a base retrieval apparatus attachable to a
stationary or movable base. In another embodiment, the apparatus
includes an aircraft docking assembly for an aircraft configured
for efficient wing-borne flight and a base retrieval apparatus
attachable to a stationary or movable base. It should be
appreciated that the present invention is not limited to the
embodiments illustrated in the figures and described below, and
that in alternative embodiments, the shape, size, configuration
and/or arrangement of one or more of the various components
described below may vary. It should also be appreciated that the
present invention need not include each and every of the components
in the embodiments illustrated in the figures and described
below.
Referring now to FIGS. 1A, 1B, 1C, 1D and 2, one embodiment of the
aircraft docking assembly and base retrieval apparatus for a
helicopter are generally illustrated. The base retrieval apparatus
includes a base station 5 having a base fuel tank 12 and a base
member 33 extending upwardly from the base fuel tank 12. The base
station 5 may include an azimuthal pivot 21, as described below. In
the illustrated embodiment, the base station 5 also includes
support member 34 connected to the base member 33 for supporting a
base docking device, fixture or probe receiver 11. A guide, funnel,
or funnel like docking receptacle 9 is attached to, and extends
upwardly from, the base docking device, fixture or probe receiver
11. The guide, funnel, or funnel like docking receptacle 9 includes
guiding surfaces. The guide, funnel, or funnel like docking
receptacle 9 has or defines a slot 10 configured to admit a cable
2, as discussed below. The support member 34 includes outwardly
extending arms 4. The arms 4 extend outwardly defining an angle. A
slot 6 is defined or placed near the vertex of the arms 4.
Aerodynamic surfaces or members 22 may be respectively attached to
the arms 4.
In one of the illustrated embodiments, the aircraft docking
assembly is attached to the helicopter and includes a cable 2, a
cable point or fixture such as a cable end fitting 3, a cable
length reducer such as a winch 7, and an aircraft docking device or
fixture such as a probe 8. The probe includes guiding surfaces and
is substantially cylindrically shaped in one embodiment. The probe
8 is attached to the helicopter and extends beyond the skids 26 of
the helicopter. At least a portion of the cable 2 is configured to
be wound around a drum of the winch 7. In another embodiment, the
winch 7 is attached to the base retrieval apparatus as described
below.
More specifically, FIGS. 1A, 1B, 1C and 1D show an illustrative
embodiment of the present invention, as used with the helicopter 1
of conventional layout. In preparation for retrieval, the
helicopter 1 deploys the lightweight cable 2 weighted by the cable
end fitting 3, and drags it between the arms 4 of the base station
5. If the helicopter's path falls within a capture
envelope--determined by, primarily, the length la, vertex angle
.psi.a, and droop angle .epsilon.a of the arms, and the length lc
of the cable (and associated height of the servicing
apparatus)--then the cable is guided into a cable holder configured
to hold the cable 2 (through the slot 6 located at the vertex of
the arms 4 as shown in FIG. 2). The helicopter pulls the cable
through the slot 6 until further motion is restrained by the cable
end fitting 3. The cable end fitting thus anchors the helicopter.
In various embodiments, the cable end fitting, cable, or slot may
be made compliant to limit shock loading. If the helicopter's path
is such that the cable misses the arms entirely, or is pulled over
an arm before reaching the slot 6, then the helicopter simply
continues in free flight, and can return for another approach.
Once the helicopter is anchored it can increase thrust, and the
cable will tend to stay nearly vertical despite disturbances. The
helicopter's position can also be regulated by appropriate control,
for example of rotor thrust and in-plane moments.
The constraint imposed by the anchored cable can be recognized by
the helicopter, and used to trigger the next retrieval step. This
involves pulling the helicopter downward toward the base docking
device, fixture or probe receiver 11, for example by activating a
winch 7 on the helicopter or on the base station. In one
embodiment, this causes the probe 8 on the helicopter to enter, and
to be guided to the base of, the guide, funnel, or funnel like
docking receptacle 9 on the base station. In one embodiment, the
funnel incorporates a cable aperture such as a slot 10 to admit the
cable, and thus allow for close placement of the cable and probe on
the helicopter. The guide, funnel, or funnel like docking
receptacle 9 guides the probe 8 to mate or match firmly with the
base docking device, fixture or probe receiver 11, thus completing
the retrieval. Mating or matching can be detected by a suitable
sensor in the probe or in the base docking device, fixture or probe
receiver 11.
Once retrieval is complete, the cable can be released from the
capture slot, and optionally retracted into the helicopter. The
helicopter's engine can be stopped. Servicing, such as provision of
electrical power, refueling from a base supply, and weighing of the
aircraft, can be effected through one or more suitable connectors
and sensors in the probe 8 and base docking device, fixture or
probe receiver 11. The helicopter can remain docked until such time
as launch is desired. These connectors can be configured to
automatically transfer fluids and/or electricity to the
aircraft.
For launch, appropriate self-testing can be completed, and the
helicopter then run-up. Release into free flight should be
permitted only when thrust is sufficient for positive separation.
This condition can be enforced by various ways, such as an
appropriately large break-out force in the docking fixture, or a
suitable combination of thrust measurement and active triggering of
an unlocking device (not shown). The aircraft would extract the
cable from the docking fixture through the slot 10 and could then
winch it onboard.
Referring now to FIGS. 3A, 3B, 3C, 3D, 4, 5, 6A, 6B, 6C and 6D, one
embodiment of an docking assembly and base retrieval apparatus for
an aircraft configured for efficient wing-borne flight is generally
illustrated. The aircraft includes a fixed wing 17, a propeller 18,
a fuselage 31, and an empennage 20. The empennage 20 includes
vertical stabilizer 27 and horizontal stabilizers 28. The aircraft
docking assembly includes cable 2, cable end fitting 3, aircraft
docking device or fixture such as a probe 8, and winch 7. In
another embodiment, the winch 7 is attached to the base retrieval
apparatus as described below. The probe 8 may include fuel and
electrical connectors 13 located at an end portion of the probe 8.
A cable guide 32 may be included to guide the cable as it is wound
from the drum of the winch 7. In the illustrated embodiment, such a
cable guide 32 is formed in the shape of a funnel.
The illustrated base retrieval apparatus for an aircraft configured
for efficient wing-borne flight includes base station 5 having a
base fuel tank 12 and a base member 33 extending upwardly from the
base fuel tank 12. The base station 5 also includes support member
34 connected to the base member 33 for supporting a base docking
device, fixture or probe receiver 11. The guide, funnel, or funnel
like docking receptacle 9 is replaced by guide or docking
receptacle 19, having edges 35 that serve to admit and orient the
empennage surfaces 27 and 28 of the aircraft as it is pulled into
base docking device, fixture or probe receiver 11, as discussed
below. The support member 34 includes arms 4. The arms 4 extend
outwardly defining an angle. A slot 6 is defined or placed near the
vertex of the arms 4. Aerodynamic surfaces or members 22 may be
respectively attached to a portion of the arms 4. In one
embodiment, the base station 5 may include an azimuthal pivot 21,
as described below.
FIG. 3 shows the aircraft 16 having a configuration suited to
efficient wing-borne flight. A propeller 18 is installed at its
nose, with the propeller's spin axis aligned with the fuselage 31.
The winch 7 and probe 8, which are comparable to those in FIGS. 1A,
1B, 1C and 1D and FIG. 2, are mounted at the rear of the fuselage
31, as shown in more detail by FIG. 4 and described above. To
prepare for retrieval, the aircraft pitches up from wing-borne
flight, with its thrust line near horizontal, into thrust-borne
flight, with its thrust line near vertical. Rotor thrust is
adjusted to balance aircraft weight. The cable 2 is then deployed,
and retrieval proceeds much as was described for the helicopter of
FIGS. 1A, 1B, 1C and 1D and FIG. 2. In this case, however, the
guide or docking receptacle 9 of FIGS. 1A, 1B, 1C and 1D and FIG. 2
is replaced by a guide or docking receptacle 19 in the form of a
set of petals whose edges 35 serve to admit and orient the
empennage surfaces 27 and 28 of the aircraft as its probe 8 is
pulled into the base docking device, fixture or probe receiver 11,
as illustrated by FIG. 5. Thus, the combination of an appropriately
long cable 2, appropriately open arms 4, and appropriately shaped
petals, permits successful retrieval across a wide range of
aircraft approach paths and orientations. After retrieval, the
aircraft can be serviced and re-launched much as was described for
the helicopter of FIGS. 1A, 1B, 1C and 1D and FIG. 2.
For automated retrieval, the aircraft and base retrieval apparatus
each can be equipped with a suitable device for measuring relative
position and velocity in three dimensions, such as
satellite-navigation equipment having antennas on the aircraft 14
and on a reference point such as point 15 near the base docking
device, fixture or probe receiver 11. In an embodiment, each of the
aircraft and base retrieval apparatus can also have equipment for
measurement of orientation, such as magnetic or inertial sensors,
as well as appropriate mechanisms for computation, power supply,
and communication.
Communication between the aircraft and base retrieval apparatus can
also be used, for example, to trigger the base retrieval apparatus
to release the cable in the event of an anomaly, such as an
excessive mismatch in position or orientation as the aircraft is
pulled toward the base docking device, fixture or probe receiver
11. In that case, the aircraft would fly clear of the base station
and could return for another approach.
In many cases, the preferred approach direction will vary with wind
velocity. This can be accommodated by providing a base retrieval
apparatus including a base station mounted on the azimuthal pivot
21 (as shown in FIG. 2). The base support member 34 could then be
oriented or rotated by a suitable actuator on the pivot, or by the
weathervane action of the suitably placed aerodynamic surfaces or
members 22.
In light to moderate wind, the preferred approach direction would
typically be upwind. However, if the wind speed V.sub.W were to
exceed the maximum airspeed V.sub.A,max at which an aircraft such
as that shown in FIGS. 3A, 3B, 3C and 3D could sustain level
thrust-borne flight, then an upwind approach would be possible only
while descending. For an approach in level flight, the procedure
illustrated in FIGS. 6A, 6B, 6C and 6D would be used instead. In
this case, the aircraft would fly into the wind at a designated
airspeed V.sub.A, while drifting downwind toward the base station
at speed (V.sub.W-V.sub.A). Capture of the cable would proceed as
described for FIGS. 1A, 1B, 1C and 1D and FIGS. 3A, 3B, 3C and 3D;
however, once anchored, the aircraft would not be able to hover
vertically above the base docking receptacle. Instead, the aircraft
could hover, and so maintain line tension, only in a downwind
kite-like position as shown in FIG. 6B.
To accommodate this situation, the base docking device, fixture or
probe receiver and the guide or docking receptacle may be mounted
on a gimbal 23 so that the axis of the funnel can align with the
cable, as shown in FIG. 6B. The gimbal could be set as desired
after the aircraft mated to the base docking device, fixture or
probe receiver, typically to thrust-vertical orientation. The
torque necessary thus to orient the gimbal can be provided by the
aircraft itself, or by an actuator on the base station. Once set at
the desired orientation, the gimbal can be locked in place by an
appropriate mechanism.
For launch in a strong wind, a downwind gimbal tilt may likewise be
necessary for the aircraft to accelerate out of the base docking
device, fixture or probe receiver upon release. In preparation for
such a downwind launch, the gimbal can be unlocked and tilted as
appropriate. The aircraft can then pull itself out of the base
docking device, fixture or probe receiver as shown in FIG. 6C. Once
clear, the aircraft could reorient if desired to reduce the
downwind drift rate, as shown in FIG. 6D. An anemometer 24 on the
base station can be used to select the appropriate orientation for
launch.
It should be understood that various changes and modifications to
the presently preferred embodiments described herein will be
apparent to those skilled in the art. Such changes and
modifications can be made without departing from the spirit and
scope of the present subject matter and without diminishing its
intended advantages. It is therefore intended that such changes and
modifications be covered by the appended claims.
* * * * *
References